The present invention relates generally to a two-part spray application system and method, and in particular to such a system and method having error protection to detect potential failures in the system.
Spray-on applications for vehicle bodies and other large objects are well known. Such applications may include, for example, primer, paint, clearcoat and foam. For foam and clearcoat in particular, the spray-on application requires the mixing of two components immediately prior to the application. In order to achieve the proper application, then, the proper ratio of the components must be supplied to the applicator.
For clearcoat, it is important that the correct ratio of resin and hardener is applied. If the ratio is too far off, then the clearcoat will not cure properly. Fixing such a problem is not easy either since a new coating of clearcoat will not adhere to the previous out-of-ratio clearcoat layer when the ratio is beyond certain limits. Consequently, when a malfunction occurs that causes out-of-ratio clearcoat to be applied, the vehicle body typically needs to be scrapped, costing time and money.
Moreover, since clearcoat is transparent, one cannot tell with an initial visual inspection immediately after spraying whether the correct mixture was applied. The out-of-ratio mixture only becomes apparent upon visual inspection after the vehicle emerges from the paint oven. This may mean 45 minutes before initially detecting a malfunction in the paint booth. During this time, a significant number of vehicles can be sprayed with the incorrect clearcoat mixture before the malfunction is detected. Thus, the problem is compounded by the fact that many vehicle bodies may be scrapped due to one malfunction in that paint booth. This problem, for example, can cause anywhere from ten to thirty vehicle bodies to be scrapped.
While current clearcoat spray application systems monitor pressure at various locations, the systems are inadequate to detect some malfunctions that cause an improper mixture of clearcoat to be applied. For example, a controller monitors pressure transducers located near outlets for the resin and hardener pumps to ensured that the outlet pressures stay below a maximum level. The controller also monitors pressure transducers located near inlets for the resin and hardener pumps to ensure that the inlet pressures stay above a minimum level. However, these systems miss some malfunctions that occur and are severe enough to cause an out-of-ratio condition for the clearcoat being applied. Such malfunctions may include, for example, a paint line downstream of a pump having a leak or a paint line coming off at the fitting of the applicator.